linux-kernel - [RFC][PATCH 00/14] VFS: Make all filesystems implement ->show

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Date:   Wed, 05 Jul 2017 16:24:01 +0100
From:   David Howells <dhowells@...hat.com>
To:     viro@...iv.linux.org.uk
Cc:     dhowells@...hat.com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [RFC][PATCH 00/14] VFS: Make all filesystems implement
 ->show_options()


Here's a set of patches that:

 (1) Removes calls to save/replace_mount_options() where the filesystem
     then implements ->show_options() anyway, ignoring ->s_options.

 (2) Makes all filesystems implement the ->show_options() superblock
     operation rather than using generic_show_options().  If necessary,
     extra information is stored in the superblock information.

 (3) Deletes save_mount_options(), replace_mount_options(),
     generic_show_options() and super_block::s_options.

This makes it easier to implement a context-based mount where the options
are passed individually over a file descriptor.  It also allows duplicate
options, options that override each other and ignored options to be
resolved rather than storing irrelevant data.

Further, a lot of the time, all the information we want to display is
stored in the super block information anyway, so the option string is
redundant.

Some things I noted whilst doing this:

 (1) A number of filesystems take uid/gid options.  Should these be
     reported relative to the observer's user namespace rather than init's
     user namespace?  After all, you can't then use those uid/gid options
     if the numbers are interpreted incorrectly if you try and forge a
     mount command from them.

 (2) Should I provide a helper for displaying uid/gid options?

 (3) How much do we need to worry about racing with remount?  Some
     filesystems happily give out the contents of the super_block without
     regard to the fact that remount might be changing it simultaneously -
     ext4, for example.

 (4) What string options actually need 'munging'?

These patches can be found here:

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=for-viro

on top of three other minor patches.

David
---
David Howells (14):
      VFS: Don't use save/replace_mount_options if not using generic_show_options
      hugetlbfs: Implement show_options
      omfs: Implement show_options
      pstore: Implement show_options
      ramfs: Implement show_options
      bpf: Implement show_options
      spufs: Implement show_options
      befs: Implement show_options
      affs: Implement show_options
      afs: Implement show_options
      isofs: Implement show_options
      9p: Implement show_options
      orangefs: Implement show_options
      VFS: Kill off s_options and helpers


 Documentation/filesystems/vfs.txt         |    6 --
 arch/powerpc/platforms/cell/spufs/inode.c |   21 +++++++--
 fs/9p/v9fs.c                              |   59 ++++++++++++++++++++++++
 fs/9p/v9fs.h                              |    3 +
 fs/9p/vfs_super.c                         |    6 +-
 fs/affs/super.c                           |   42 +++++++++++++++--
 fs/afs/super.c                            |   45 ++++++++++++++++++-
 fs/befs/linuxvfs.c                        |   24 +++++++++-
 fs/btrfs/super.c                          |    1 
 fs/debugfs/inode.c                        |    2 -
 fs/efivarfs/super.c                       |    1 
 fs/hugetlbfs/inode.c                      |   70 +++++++++++++++++++++++------
 fs/isofs/inode.c                          |   51 ++++++++++++++++++++-
 fs/isofs/isofs.h                          |    3 +
 fs/namespace.c                            |   59 ------------------------
 fs/omfs/inode.c                           |   33 ++++++++++++--
 fs/orangefs/super.c                       |   15 ++++++
 fs/pstore/inode.c                         |   14 +++++-
 fs/pstore/internal.h                      |    3 +
 fs/pstore/platform.c                      |    2 -
 fs/ramfs/inode.c                          |   32 +++++++++----
 fs/reiserfs/super.c                       |    4 --
 fs/super.c                                |    1 
 fs/tracefs/inode.c                        |    2 -
 include/linux/fs.h                        |    9 ----
 include/linux/hugetlb.h                   |    3 +
 include/net/9p/client.h                   |   13 +++++
 include/net/9p/transport.h                |    1 
 kernel/bpf/inode.c                        |   16 +++++--
 net/9p/client.c                           |   25 ++++++++++
 net/9p/trans_fd.c                         |   31 ++++++++++++-
 net/9p/trans_rdma.c                       |   31 ++++++++++++-
 32 files changed, 481 insertions(+), 147 deletions(-)